Technical Field
The present invention relates to a mobile radio communication terminal and a method of operating a mobile radio communication terminal. It also relates to a base station and an operating method for a base station and to a mobile radio communications infrastructure and an operating method for a mobile radio communications infrastructure.
Description of the Related Art
Selection of a suitable mobile network cell by a mobile radio communication terminal according to the received signal strength is known from WO 00/13377. When a suitable cell has been found, the mobile radio communication terminal logs into the assigned access network via the respective cell. A base station used for this purpose is then used by the mobile radio communication terminal as the currently serving/selected base station. The mobile radio communication terminal regularly checks, also after logging in, whether there is a mobile network cell providing better reception. When this is the case, the better cell is selected.
Measurements for such cell reselection by the terminal are carried out in all states of the mobile radio communication terminal in which the user equipment can perform a cell change autonomously. In addition to an inactive state referred to as “IDLE,” these states may include other states known in UMTS or other mobile communications technologies, such as Cell PCH or URA-PCH. This inactive state is periodically interrupted in order to check whether signals directed at the mobile radio communication terminal are received from the external base station. Such signals are typically paging signals that are transmitted on a special signaling channel. The paging signals are transmitted at specific times. The interval between successive transmissions of paging signals defines a “discontinuous reception period,” or “DRX period” for short. WO 00/13377 describes that the DRX cycle duration may differ in length, and proposes that the number of measurements for cell selection be chosen according to the respective DRX cycle duration.
Within a cell, however, the cycle duration of the DRX cycle is identical for all mobile radio communication terminals that are in a state allowing autonomous cell selection. This applies for both second-generation radio communication standards (GSM) and for third generation radio communication standards (UMTS). The DRX cycle duration is typically made dependent on the characteristic features of a specific mobile network cell, for example of an environment in which that cell is located. For example, a shorter DRX cycle duration is chosen in an urban environment so that mobile radio communication terminals that would have to switch to a different cell within a short time, for example when moving into a subway station, are able to make that change without noticeable delays. A longer DRX cycle is prescribed, in contrast, by mobile network cells in environments that allow longer parallel reception of the serving cell and a neighboring cell, and which can therefore provide a longer time for changing cells without delays. More specifically, these may be mobile network cells of greater geographical expanse, in which a mobile radio communication terminal typically spends a longer time.
One disadvantage is that a DRX cycle duration which may be unreasonably short or unreasonably long is assigned in this way to mobile radio communication terminals independently of the behavior of their users and independently of the purpose for which it is being used. For example, a vending machine that is connected via a radio modem to a service headquarters and which is installed in an urban environment must operate with a very short DRX cycle duration. This necessitates frequent activation of the radio modem from an inactive state, and also requires measurement of neighboring cells at respective intervals that are unreasonably short for the radio modem in this application.
The shorter the DRX cycle duration, the higher is the average power consumption of a mobile radio communication terminal, since the durations of the activity and inactivity periods of a mobile radio communication terminal are defined on the basis of the DRX cycle duration.
WO 2007/080399 A1 describes mobile radio communication terminals that are installed in a vending machine or in a vehicle or in an alarm system. In the core network, a “terminal type identifier” TTID is set for such stationary terminals to “FIXED” and communicated to the access network. According to the message sequence shown in FIGS. 2A/2B, this TTID parameter is sent in an “insert subscriber data” message 122 in response to a location update message by HRR/HSS to the assigned serving GPRS support node SGSN. The SGSN then instructs the mobile radio communication terminal with a GMM attach accept message 128 not to perform any more periodic location updates.